Need Help With A Code 22

Sam_93Cobra · Jan 19, 2017

Heya, first post
I'm trying to figure out a code 22 on my 93.
Ive read some great advice here, and here's what I know:

Replacing the MAP did not cure the code. I used a new Motorcraft MAP.
The MAP is not incorrectly connected to a vacume hose
When the harness is disconnected from the MAP, 5volts are present at both the black wire and the green signal wire (I've read some conflicting info about the proper voltage of the green wire as 5v or 0v).

The resistance between the black wire and the same wire at the TPS and EGR is about 1ohm

However the resistance between the black wire and the neg. battery cable is quite high. This may be the problem, but Im not sure where to dive in to fix it.

Any advice?

jrichker · Jan 20, 2017

Sam_93Cobra said:
Heya, first post
I'm trying to figure out a code 22 on my 93.
Ive read some great advice here, and here's what I know:

Replacing the MAP did not cure the code. I used a new Motorcraft MAP.
The MAP is not incorrectly connected to a vacume hose
When the harness is disconnected from the MAP, 5volts are present at both the black wire and the green signal wire (I've read some conflicting info about the proper voltage of the green wire as 5v or 0v).

The resistance between the black wire and the same wire at the TPS and EGR is about 1ohm

However the resistance between the black wire and the neg. battery cable is quite high. This may be the problem, but Im not sure where to dive in to fix it.

Any advice?

Signal ground troubleshooting 91-93 5 Mustangs

The computer pin 46 signal ground is a critical component: it provides ground for the Baro, TPS, ECT, EGR position sensor and ACT. Signal ground is used in many circuits that have analog inputs to isolate the electrical noise. It is always separate from power ground, although both may have a common connection origination point. Signal ground usually has some conditioning that reduces the electrical noise to prevent false readings
The gray/red wire (pin 46) is signal ground for the computer. It provides a dedicated ground for the EGR, Baro, ACT, ECT, & TPS sensors as well as the ground to put the computer into self-test mode. If this ground is bad, none of the sensors mentioned will work properly. That will severely affect the car's performance. You will have hard starting, low power and drivability problems. What sometimes happens is that the test connector gray/red wire gets jumpered to power which either burns up the wiring or burns the trace off the pc board inside the computer. That trace connects pins 46 to pins 40 & 60.

See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix to the computer internal signal ground.

If the ground for the TPS goes bad, the TPS output voltage increases and the idle speed goes up.

Troubleshooting signal ground problems:
Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter.
1.) With the power off, measure the resistance between the computer test ground
(Gray/red wire) on the self test connector and battery ground. You should see less than
1.0 ohms.

2.) MAP circuit: Check the resistance between the gray/red wire on the MAP/BARO sensor and then the gray/red wire on the EGR and the same wire on the TPS. It should be less than 1 ohms. Higher resistance than 1 ohms indicates a problem with the 10 pin connector or the splice inside the main harness where the wire from the 10 pin connectors joins the rest of the gray/red wire. Next check the resistance between the gray/red wire and the negative battery cable. It should be less than 2.0 ohms.

3.) Engine mounted sensor circuit: Check the resistance between the gray/red wire on the TPS and battery ground. It should be less than 2.0 ohms. Higher resistance than 2.0 ohms indicates a problem with the 10 pin connector or the splice inside the main harness where the wire from the 10 pin connectors joins the rest of the gray/red wire.

The gray/red wire and black wire are the same wire. The wire color may be different in cars from 91 to 93.

B.) MAP/Baro circuit: check the resistance between the black/white wire on the MAP/Baro sensor and the negative battery cable. It should be less than 1.5 ohms. If it isn’t you can figure that you have serious problems with the wiring for the computer or the computer’s internal signal ground. Check the resistance between the black/white wire on the MAP/Baro sensor and then the black/white wire on the EGR and the same wire on the TPS. Repeat the process with the black/white wire on the ACT & ECT sensors and the MAP/Baro sensor black/white wire It should be less than 1 ohms. Higher resistance than 1 ohms indicates a problem with the 10 pin connector or the splice inside the main harness where the wire from the 10 pin connectors joins the rest of the black/white wire

See the graphic for the 10 pin connector circuit layout.

The injector power pin is the VPWR pin in the black 10 pin connector.

[/indent]

3.) Testing the computer's internal signal ground:
Remove the passenger side kick panel and disconnect the computer connector. There is a 10 MM bolt that holds it in place. Measure the resistance between the black/white wire and pin 46 on the computer wiring connector: it should be less than 1.5 ohms. More that 1.5 ohms is a wiring problem. If it reads 1.5 ohms or less, then the computer is suspect. On the computer, measure the resistance between pin 46 and pins 40 & 60: it should be less than 1.5 ohms. More than that and the computer’s internal ground has failed, and the computer needs to be repaired or replaced.

See http://www.stangnet.com/mustang-forums/749974-computer-issue.html#post7490537 for Joel5.0’s fix to the computer internal signal ground.

If the ground for the TPS goes bad, the TPS output voltage increases and the idle speed may fluctuate..

Davedacarpainter · Jan 20, 2017

I'll jus sneak your thread over to the tech side.

Welcome to stangnet btw.

Sam_93Cobra · Jan 20, 2017

Thanks Jrichker, that's a lot of info!

I'm working down your list. Ive tested all but the computer at this point.
So far all of the resitance values pass, except I get high and variable values between the black/white wire at the MAP and the following: the neg. battery cable, the ACT and the ECT

When testing the computer pins, do i test the female or the male "pins"? I can barely see up into the slot for the male pins.

jrichker · Jan 20, 2017

Sam_93Cobra said:
Thanks Jrichker, that's a lot of info!

I'm working down your list. Ive tested all but the computer at this point.
So far all of the resitance values pass, except I get high and variable values between the black/white wire at the MAP and the following: the neg. battery cable, the ACT and the ECT

When testing the computer pins, do i test the female or the male "pins"? I can barely see up into the slot for the male pins.

You may end up having to either remove the computer , 2 screws, but they somewhat difficult to reach.

The following are diagrams courtesy of Tmoss & Stang&2birds

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs

Sam_93Cobra · Jan 21, 2017

Ok, Ive gone through all the resistance tests, even on the computer and it all checks out fine. The problems I reported earlier came from confusion on one of the wire colors, but your diagram fixed that. Im starting to wonder if I have bad enough luck to,have bought a defective, new MAP!

One thing I did find by accident, the brown/white wires on the MAP circuit have some resistance reading (though intermitent and quite high) with both the black/white grey/red wires on the MAP curcuit and comp connector pin 46 (with comp removed). Could that indicate a short?

jrichker · Jan 21, 2017

Let's stop and clarify some terms.

Short or short circuit - when power or signal bypasses the intended path and makes a low resistance connection to power or ground or some other circuit.

Open or open circuit - when there is a break in the wiring or connection between component of a circuit. That break could be in the power or ground or signal connection.

High resistance in Ohms ( Ω ) is resistance between components or in a component that exceeds the limits for proper operation of the circuit or device.

High resistance is were you are at now. You may have a break in the wiring or a loose connection. Put one ohmmeter lead on the suspect MAF wire an the other on the computer wiring harness pin that it connects to. Turn the ohmmeter to continuity; on most meters it makes a sound then there is good continuity. Then start wiggling wires and connections in the MAF circuit until you hear the meter stop making its "OK I have continuity sound.".

General karthief · Jan 22, 2017

jrichker said:
Let's stop and clarify some terms.

Short or short circuit - when power or signal bypasses the intended path and makes a low resistance connection to power or ground or some other circuit.

Open or open circuit - when there is a break in the wiring or connection between component of a circuit. That break could be in the power or ground or signal connection.

High resistance in Ohms ( Ω ) is resistance between components or in a component that exceeds the limits for proper operation of the circuit or device.

High resistance is were you are at now. You may have a break in the wiring or a loose connection. Put one ohmmeter lead on the suspect MAF wire an the other on the computer wiring harness pin that it connects to. Turn the ohmmeter to continuity; on most meters it makes a sound then there is good continuity. Then start wiggling wires and connections in the MAF circuit until you hear the meter stop making its "OK I have continuity sound.".

I need a course in electrical circuits for dummies.
Only thing I know for sure is positive, negative, and water runs down hill.

Sam_93Cobra · Jan 22, 2017

Yes, I should have worded that more carefully.

The continuity audio alarm does not sound when connecting across the brown/white and black/white circuits, or the brown/white and the 46 pin, but I do get a resistance reading (intermittent and high, >50 ohms), so some electrons are flowing. I tested this today however and that is simply the resistance of the devices on those two circuits, such as the TPS, which gives a similar reading when I test it individually.

I'm back to the MAP sensor itself.

liljoe07 · Jan 22, 2017

You really need a meter that reads hertz to check the MAP/BP sensor correctly.

jrichker · Jan 22, 2017

karthief said:
I need a course in electrical circuits for dummies.
Only thing I know for sure is positive, negative, and water runs down hill.

Since you have said that you have a low level of proficiency in electrical matters, here's some help before you get started.

Automotive circuits are mostly simple stuff: a power source, a connection path, a control device, a load, and a ground.
The battery/alternator is the positive power source.
The wire, and fuses are the connection path.
Control devices are switches, relays and sensors.
A load is a light, motor, solenoid, relay coil or heater element.
In automotive circuits, grounds are the return connection path so the electrical power can flow from the load to the negative side of the power source.

Electricity flows like water:
Voltage is like pressure,
Current in amps is like volume,
Resistance is like the kink you put in a garden hose to decrease the pressure or volume.
Power is pressure multiplied by volume or voltage multiplied by current (amps)

Digest that, and you just got the first 3 days of Electricity 101.

Use some jumper wires (connection path and ground) to hook up a switch (control device), a battery (power source), a light bulb (load). Now make the light turn on and off with the switch.

That's the electrical lab for the first week of Electricity 101.

For free automotive electrical training, see Automotive Training and Resource Site . Once you are there, select online instruction. I have personally reviewed the material and it is very good. If you are new to automotive electrical troubleshooting, I highly recommend you spend a hour or so going through the material. You'll save at least that much time troubleshooting problems.

General karthief · Jan 22, 2017

jrichker said:
Since you have said that you have a low level of proficiency in electrical matters, here's some help before you get started.

Automotive circuits are mostly simple stuff: a power source, a connection path, a control device, a load, and a ground.
The battery/alternator is the positive power source.
The wire, and fuses are the connection path.
Control devices are switches, relays and sensors.
A load is a light, motor, solenoid, relay coil or heater element.
In automotive circuits, grounds are the return connection path so the electrical power can flow from the load to the negative side of the power source.

Electricity flows like water:
Voltage is like pressure,
Current in amps is like volume,
Resistance is like the kink you put in a garden hose to decrease the pressure or volume.
Power is pressure multiplied by volume or voltage multiplied by current (amps)

Digest that, and you just got the first 3 days of Electricity 101.

Use some jumper wires (connection path and ground) to hook up a switch (control device), a battery (power source), a light bulb (load). Now make the light turn on and off with the switch.

That's the electrical lab for the first week of Electricity 101.

For free automotive electrical training, see Automotive Training and Resource Site . Once you are there, select online instruction. I have personally reviewed the material and it is very good. If you are new to automotive electrical troubleshooting, I highly recommend you spend a hour or so going through the material. You'll save at least that much time troubleshooting problems.

Sorry, I was in a sarcastic mood although it is fairly accurate measurement of my electrical experience, I have the above notes taped to the wall above my bench and will take the online course you recomended, your knowledge and ability to explain things are the reason my junk runs as good as it does,
Please excuse me, I am not really a boob but I play one on sn

jrichker · Jan 22, 2017

karthief said:
Sorry, I was in a sarcastic mood although it is fairly accurate measurement of my electrical experience, I have the above notes taped to the wall above my bench and will take the online course you recomended, your knowledge and ability to explain things are the reason my junk runs as good as it does,
Please excuse me, I am not really a boob but I play one on sn

I am glad to help.
I seem to have become the auto shop teacher that everyone wishes that they had in high school...

General karthief · Jan 22, 2017

I bet you would've been great.

Sam_93Cobra · Jan 29, 2017

Ok, follow up post:

I installed the second, new motorcraft MAP (these are really BAP sensors), same model number as the first, and it works!! No codes.

It took a lot of testing to get here and even though the problem turned out to be two faulty sensors I'm thankful for all the tech advice. Jrichker you are great at this!

Have a good 5.0 day folks,

jrichker · Jan 29, 2017

Sam_93Cobra said:
Ok, follow up post:

I installed the second, new motorcraft MAP (these are really BAP sensors), same model number as the first, and it works!! No codes.

It took a lot of testing to get here and even though the problem turned out to be two faulty sensors I'm thankful for all the tech advice. Jrichker you are great at this!

Have a good 5.0 day folks,

I am glad to be of service. I hope that you have some dry, sunny days so that you can enjoy all your hard work...

Need Help With A Code 22

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wonder how much it would cost to ship you a pair

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